JPS63224055A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To prevent the deterioration of the magneto-optical characteristics even in a high humid environment by forming a protective film of a thermoplastic resin. CONSTITUTION:A protective film 4 formed on a recording layer 3 of a rare earth element-transition metal alloy is made of a pinhole-free thermoplastic resin capable of preventing the permeation of the air and moisture in the air e.g., poly-p-xylylene or polystyrene. Since the protective film 4 contains no oxygen, the recording layer 3 is not oxidized. Since the film 4 has no pinholes, when the resulting recording medium is used in the air, the permeation of the open air into the recording layer 3 is prevented by the film 4 and the characteristics of the medium are stably maintained over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in magneto-optical recording media used in magneto-optical disks and the like.

[Conventional technology]

Magneto-optical disks, which use laser light to record information using the photothermal magnetic effect and reproduce recorded information using the magnetic Kerr effect and Faraday effect, are capable of high recording density and high-speed access, and are also capable of erasing and reproducing recorded information. It is expected to be put to practical use because recording can be performed repeatedly. In particular, TbPe, Tb
Rare earth-transition metal alloys (hereinafter R) such as FeCo and GdFe
Magneto-optical recording media that use an amorphous perpendicularly magnetized film (abbreviated as E-TM alloy) as a recording layer have been developed because it is easy to form a thin film with a large area and has good writing and reproduction sensitivity. It's promising. However, R,B-TM
Magneto-optical recording media with a gold alloy recording layer also have the disadvantage that their magneto-optical properties deteriorate when used in a humid atmosphere due to the corrosion resistance of the RE-TM gold alloy. .

In contrast, it is common to provide a protective film on the recording layer to prevent the recording layer from coming into direct contact with the atmosphere. For example, FIG. 2 is a schematic cross-sectional view showing the main parts of a conventionally used magneto-optical recording medium.

In FIG. 2, this magneto-optical recording medium is made of a plastic substrate 1 made of polycarbonate or the like, and in order to increase writing sensitivity and reproduction sensitivity, a material having a higher refractive index and lower thermal conductivity than the substrate 1, such as S t O, S l 3N.

For example, TbFe, TbFeC, etc. are formed by interposing a transparent thin film layer 2 such as Zn8 (hereinafter abbreviated as a second layer).
o.

A recording layer 3 of a RE-TM alloy thin film such as GdFe is formed, and S io, 8 ioz, Si
By providing the protective film 4 made of 3N4 or the like, the recording layer 3 is not directly exposed to the atmosphere and its characteristics are prevented from deteriorating due to the environment. Note that the arrow indicates the direction of travel of the laser beam. Also, although not shown, the enhancement layer 2
without forming the substrate l.

Recording layer 3. A magneto-optical recording medium in which protective films 4 are laminated in this order is also used.

[Problem that the invention seeks to solve]

However, in order to put these magneto-optical recording media into practical use, there is a problem in which the protective film 3 must be improved. In other words, the protective film 3 using Sin, SiO3°813N4, etc. is formed as an extremely fine thin film without pinholes, and it is inevitable that many pinholes will be generated. Therefore, in practice, the medium cannot completely prevent the atmosphere and moisture in the atmosphere from penetrating into the recording layer 3 through these pinholes.

In addition, when oxides such as SiO or Si02 are used for the protective film 4, the oxygen components thereof react with the recording layer 3, causing deterioration of the magneto-optical characteristics.
When a nitride such as No. 4 is used as the protective film 4, a reactive sputtering method is used as a film forming method, which causes disadvantages such as a complicated cracking process and an increased cost.

Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks and provide a magneto-optical recording medium equipped with an excellent protective film that does not allow moisture to pass through and does not deteriorate the magneto-optical properties even when placed in a high humidity environment. It's about doing.

[Means for solving problems]

The present invention uses a thermoplastic resin that has no pinholes and can prevent penetration of the atmosphere and moisture contained in the atmosphere, as a protective film provided on the R, E-TM gold alloy recording layer of a magneto-optical recording medium. For example, this was achieved by using polyparaxylylene or polyethylene.

[Effect]

The protective film of the present invention is a thermoplastic resin such as polyparaxylylene or polysmolene, and since the protective film itself does not contain oxygen, the recording layer is not oxidized, and this protective film does not have pinholes. Therefore, when a magneto-optical recording medium equipped with this protective film is used in the atmosphere, it prevents outside air from entering the recording layer and maintains stability for a long period of time without damaging the characteristics of the medium. It is something to do.

〔Example〕

The present invention will be explained below based on examples.

The configuration of the magneto-optical recording medium obtained by the present invention is exactly the same as the cross-sectional view of the deaf shown in FIG. The difference is that a thermoplastic resin is used as the protective film 4.

Next, a method for manufacturing the magneto-optical recording medium of the present invention will be described. FIG. 1 is a system diagram showing an outline of the magneto-optical recording medium manufacturing apparatus of the present invention together with the arrangement of each component device. In FIG. 1, the entire apparatus includes an evaporation chamber 59 a decomposition chamber 6. Vapor deposition chamber7. A cooling trap 9 and a rotary pump 10 are connected to the sputtering chamber 8°. The cooling trap 9 and rotary pump 10 are a common exhaust system for this entire device.

To explain this in conjunction with FIG. 2, in the sputtering chamber 8, on a sufficiently degassed polycarbonate substrate l, for example, T b 2 g having an axis of easy magnetization perpendicular to the polycarbonate substrate l is placed.
An amorphous magnetic thin film of Fe ss CO12 is formed as the recording layer 3. On the other hand, in the evaporation chamber 5, dip-xylylene is evaporated at a temperature of 175° C. and a vacuum degree of I Torr, and then led to a decomposition chamber 6, where a temperature of 680° C. and a vacuum degree of 0.0 Torr are introduced.
It is decomposed into para-silylene monomer under the condition of 5 Torr, and the thermally decomposed monomer is sent to the vapor deposition chamber 7. At the same time, by introducing the substrate l provided with the recording layer 3 as described above into the vapor deposition chamber 7 without breaking the vacuum state, the temperature is 25.
℃, vacuum level 0°5 Torr vapor deposition chamber 7
Para-xylylene monomer is attached to the surface of the recording layer 3 within the recording layer 3, and a poly-para-xylylene film having a thickness of 2,000 to 5,000 thick can be formed as the protective film 4. At this time, the surface of the substrate 1 on which the laser beam is incident is covered with a mask. Note that the above method is naturally applicable to the recording layer of a magneto-optical recording medium in which the second layer 2 described above is not formed.

The thus obtained magneto-optical recording medium was heated to a temperature of 60°C.

As a characteristic change of this medium after being left in a constant temperature and constant weight bath at 90% humidity for 100 hours, the increase rate of the Kerr rotation angle Ok of the recording layer 3 with respect to the initial value was investigated and the result was 10'%. This value is approximately 1/2 of the rate of change in the Kerr rotation angle Ok of approximately 20% obtained when a conventional magneto-optical recording medium with a thickness of 2000 Å of SiO formed as the protective film 4 is tested under the same conditions. be. From this, it can be concluded that the magneto-optical recording medium in which the recording layer 3 is coated with polyparaxylylene as the protective film 4 according to the present invention has sufficient usability not only in the environment in which it is normally used, but also in an environment with slightly high humidity. can be judged.

In this embodiment, only polyparaxylylene has been described as the material for the IWA, but the same effect can be obtained by using other thermoplastic resins such as polystyrene.

〔Effect of the invention〕

The oxide thin film conventionally used as a surface protective film for magneto-optical recording media with an amorphous perpendicular magnetization film of rare earth-transition metal alloy as the recording layer inevitably generates pinholes. In contrast, the magneto-optical recording medium of the present invention uses a thermoplastic resin such as polyparaxylylene as a protective film. After the recording layer is formed, the layers are stacked without breaking the vacuum, and no pinholes are generated in the resulting protective film, so even when this medium is left in the atmosphere, moisture in the atmosphere will not reach the recording layer. without reaching
In addition, since this protective film itself does not contain oxygen, there is no risk of oxidizing the recording layer, and therefore the magneto-optical properties do not deteriorate, making it possible for magneto-optical recording media to maintain stable and good properties over a long period of time. is obtained.

[Brief explanation of drawings]

FIG. 1 is a layout diagram for explaining a magneto-optical recording medium manufacturing apparatus of the present invention, and FIG. 2 is a cross-sectional view of the main part of the magneto-optical recording medium. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Ennoonce layer, 3...Recording layer, 4...Protective film, 5...Evaporation chamber, 6...Decomposition chamber, 7...Vapor deposition chamber. 8... Sputtering chamber, 9... Cooling trap, 10...
Row 1 Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1) In a magneto-optical recording medium in which a protective film and a recording layer having an axis of easy magnetization perpendicular to the main surface of the substrate are laminated on a substrate, a thermoplastic resin is used as the protective film. A magneto-optical recording medium characterized by: 2) A magneto-optical recording medium according to claim 1, wherein the thermoplastic resin is polyparaxylylene. 3) A magneto-optical recording medium according to claim 1 or 2, wherein the protective film is formed by vacuum deposition.